Re: [PATCH 8/9] dt-bindings: reserved-memory: MediaTek: Add reserved memory for SVP

On Wed, 2023-11-01 at 11:20 +0530, Jaskaran Singh wrote:

 	 
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 On 10/20/2023 3:20 PM, Yong Wu (吴勇) wrote:

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On Thu, 2023-10-19 at 10:16 +0530, Vijayanand Jitta wrote:

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Instead of having a vendor specific binding for cma area, How

about

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retrieving

https://lore.kernel.org/lkml/1594948208-4739-1-git-send-email-hayashi.kunihiko@socionext.com/ (local)

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 ?
dma_heap_add_cma can just associate cma region and create a heap.

So,

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we can reuse cma heap
code for allocation instead of replicating that code here.

Thanks for the reference. I guess we can't use it. There are two
reasons:
  
a) The secure heap driver is a pure software driver and we have no
device for it, therefore we cannot call dma_heap_add_cma.
  

Hi Yong,

We're considering using struct cma as the function argument to
dma_heap_add_cma() rather than struct device. Would this help
resolve the problem of usage with dma_heap_add_cma()?

Yes. If we use "struct cma", I guess it works.

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b) The CMA area here is dynamic for SVP. Normally this CMA can be

used

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in the kernel. In the SVP case we use cma_alloc to get it and pass

the

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entire CMA physical start address and size into TEE to protect the

CMA

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region. The original CMA heap cannot help with the TEE part.

Referring the conversation at

https://lore.kernel.org/lkml/7a2995de23c24ef22c071c6976c02b97e9b50126.camel@mediatek.com/ (local)

;

since we're considering abstracting secure mem ops, would it make
sense
to use the default CMA heap ops (cma_heap_ops), allocate buffers from
it
and secure each allocated buffer?

Then it looks you also need tee operation like tee_client_open_session
and tee_client_invoke_func, right?

It seems we also need change a bit for "cma_heap_allocate" to allow cma
support operations from secure heap.

I will send a v2 to move the discussion forward. The v2 is based on our
case, It won't include the cma part.

Thanks,
Jaskaran.

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Thanks.

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Thanks,
Vijay